Gas-filled tube type of relaxation oscillator system



Oct. 7, 1947. A. H. DICKINSON ,4

GAS-FILLED TUBE TYPE OF RELAXATION OSCILLATOR SYSTEM Filed June 19, 19452 Sheets-Sheet 1 ans FILLED 3036 ans f/LLED I I 3 J 6e INVENTOR'ATLI'OIRNEY Oct. 7, 1947. A. H. DICKINSON GAS-FILLED TUBE TYPE OFRELAXATION OSCILLATOR SYSTEM Filed June 19, 1943 2 Sheets-Sheet 2 I wwmwww ummQ\wmvh w&m mm\ Patented Oct. 7, 1947 GAS-FILLED TUBE TYPE OFRELAXATION OSCILLATOR SYSTEM Arthur H. Dickinson, Scarsdale, N. Y.,assignor to International Business Machines Corporation, New York, N.Y., a corporation of New York Application June 19, 1943, Serial No.491,440

8 Claims.

This application relates to electrical oscillators and is acontinuation-in-part of my copending application Serial No. 314,767,filed January 20, 1940.

An object of the invention is to provide means to keep an oscillator indesired synchronism despite changes in its phase or frequency or both.

Another object is to provide means to keep an oscillator in synchronism,when operating at different frequencies and phases, in combination witha circuit network to change the frequency and phase automatically,

Another object is to provide means to keep in synchronism a group ofoscillators, each having either a different frequency or phase.

Another object is to provide means whereby commonly synchronizedoscillators are prevented 1 from reacting upon each other.

Other obects of the invention will be pointed out in the followingdescription and claims and illustrated in the accompanying drawings,which disclose, b way of example, the principle of the invention and thebest mode, which has been contemplated, of applying that principle.

In the drawings:

Fig. 1 shows a circuit network embodying the invention, and

Fig. 2 is a timing chart showing waves generated by the oscillators.

The apparatus exemplifying my invention includes a primary synchronizingmeans which is preferably an electrical oscillator, hereafter called themain oscillator. Intermediate oscillators are synchronized by the mainoscillator, these intermediate oscillators being adjusted to operate indifferent phase relation but at the same frequency, such frequency beinga selected submultiple of the main oscillator frequency. Theintermediate oscillators synchronize a plurality of other oscillatorswhich may be called, for convenience, tertiary oscillators. The latterare synchronized for operation at the same frequency but in differentphase, such frequency being a selected submultiple of the intermediateoscillator frequency and, hence, a smaller submultipl of the mainoscillator frequency. A variable frequency and phase oscillator isdirectly synchronized by the main oscillator. A control network isprovided for automatically changing frequency of this variableoscillator. The waves generated at the changed frequency have differentphases than the waves which were generated at the previous frequency,The control network also functions automatically to return the variableoscillator to operation at the previous fre- 2 quency. The waves thengenerated will have either the same or a different phase than the wavespreviously produced at this frequencydepending on the duration of theintervening operation at the changed frequency. Operation of the controlnetwork is governed selectively by the tertiary oscillators. Thevariable oscillator frequencies are all submultiples of the mainoscillator frequencies.

As illustrative, relaxation oscillators are used but it will beunderstood that other suitable electrical oscillators may be used.

A relaxation oscillator includes a condenser, an impedance through whichit is charged, and a short circuiting device to cause its discharge.

The charging period is relatively gradual, while the discharging periodis substantially instantaneous. The charge and discharge of thecondenser are repeated periodically, and saw-toothed. waves aregenerated. In the present case it is.

varied or regulated to determine at what anode.

potential the gas tube is to fire and short circuit the condenser. In amanner explained later, the

grids of the gas tubes contained in the oscillatorsv to be synchronizedreceive an increment of synchronizing voltage, reducing the grid bias ofthese tubes. The anode voltage of these tubes is determined by thevoltage across the related condensers. has reached a critical valuecoordinate with the reduced grid bias will ignite in response to theincrement of synchronizing voltage.

Fig. 1 shows circuits which are generally similar to circuits found inmy said copending application and, wherever convenient, correspondenceof parts will be indicated by using the same reference characters as inthe copending application.

In detail, plus and minus lines I and 2 are connected to a suitabl D. C.supply. The upper part of Fig. 1 shows, at the left, the mainoscillator, which will be identified as 22m26m, and at the right, twointermediate oscillators which will be The three- Only those tubes whoseanode potential identified as 22g-261g and, 22h-26h. The middle part ofFig. 1 shows two tertiary oscillators 22a26a, and 22e--26e, flanking twotriodes and related elements. The bottom part of Fig. 1 shows thevariable oscillator 22-26 and the control network for automaticallycharging its frequency or. phase or both. Since all the oscilla: torsare ofthe same nature, only one needbe described in essential detail,The others will be de scribed only in respect to features peculiar tothemselves. Similar parts ofthe; differentoscib lators will berecognized by common reference numbers applied thereto.

The main oscillator will be described. indetail.

This oscillator includes condenser. ZZm-conriected'...

via resistance 27m in series with pentode 23m and in parallel with gastube 26m. Pentode 23m has its control grid connected to line 2and-isself-biased by respectively coarsely and finely ad.- J'ustable resistors24m and 25m. The screen grid of. thepentode is connected to point 33mbetween resistors 34m and35m serving as, a volte age: divider acrosslines I and 2. The return circuit of'the control grid, of the gas tubeis through resistance 3lm tonpoint 33m and thence Via resistor -35m, toline 2. Thus, the voltage at pointz3'3m'determinesboththe screen voltageof the'pentode and the; grid bias of; the gas'tube: A.

suitablefrequency for the oscillator-may be. see lected by changing theadjustment-of: one or more of'the following. condenser 2.2m, resistance2am, and resistance V2 5112. When the voltage across. the condenser,reaches criticalvalue for the main tainedgrid bias of' the gas tube,this tubefires, short" circuiting the condenser:

the potent-i'al'at point 6m: Following the discharge, thecondenser'begins to recharge; and

The grid ofjthe. gas tube 269 is connected by re:

sistor 3l.g to .point 395g of a voltage divider com.- prised ofresistances 333g and 32g, Resistance 32g is, wired to point. 339 of thevoltage divider 349,-359 of the oscillator 229-2691. Resistance 3.039is. coupled. by condenser 302g to wire 313i. whichconnects to .point Simofthe. main oscillator. In the. absenceof a pulse of rising voltage onpoint 6m,, thev potential, at point. 3.959,. is relatively low and thegridbiasof .tube 25g .is.then.at. what may. be. called anormal value,Upon eachsharprisein voltage on ,pointfim, it. transmitsapulse via.line. 3,01 and condenser 30.2 to voltage divider. 3 3954295,momentarilyapply-in ian incrementof voltageto point 305a,. Thisincrementof.voltage. supplementsthe normal-voltage. on the: grid of. tube 26g.-to reduce the grid biasbelow normal. value. Thereupon, thetubelfigtendsto ignite, but. whether: this actually takessplace depends on Wheher theanode, potential-- of. tube 26g, determined; by the potential. acrossthe condenser 2211; has; reachedtherequisite ionizing-.- value inrelation tothe; momentarily reduced grid. bias of the tube.

Similarly; point. iimtransmits synchronizing pulsesof: positive voltagevia: line-301 and. acondensen Bil-2hrtel-the intermediate: oscillator22-h*-- H1 andaviarline 3zlfland'condenser 3B2tothe variable oscillator-2'2.='2-61-. Ina, similar manner;

Such discharge is-substantially instantaneous and sharply raises the ridof tube 25a receives synchronizing pulses 7 point 6h act throughcondenser 382e, to reduce the grid'bias: of. tube 256, while with theswitch in the reverse position, the pulses on point to act through thiscondenser upon the grid of the tube 262.

Toaid; in the further description, the operations of the oscillatorswill be referred to a common chosen time base or cycle. This cycle ishere chosen, for convenience, as the cycle of the variable oscillator2226 during itsoperation at the lower of two frequencies. Forconvenience, such lower frequency may be called the base. frequency. Acomplete oscillation at the basefrequency requires one cycle period, asindicated in cycle I]? of Fig. 2. The variable oscillator, ina;

manner explained later, is shiftable automatically to a frequency doublethe base frequency; This shift, ifoccurring an odd number of indexpoints from'thepeak of thebase oscillation causes the double frequencyoscillations to be phased at mid-index points, as indicated bythepartially dotted waves at the bottom of Fig. 2; If the shift occursat an even number of index pointsfrom the .peak of the base oscillation,the double frequency oscillations have an exact index point phaseasindicated by the .partially dotted wave inthe' next to last timing lineof Fig. 2.. Thus, the base oscillations of the variable'oscillator, mayhave any exact point phase while the double frequency oscillations mayhave any exact index point 07" any mid-index point phase. In all,.withthe example chosen, there are twenty possible phases of the variableoscillator, ten exact index point phases and ten mid-index point phases.The scheme of my invention accordingly provides, for the chosen example,at least twenty synchroniz= ing pulses a. cycle, each potentiallycapable. of synchronizing the variable oscillator in any, of its twentypossible phases and at either of its two frequencies. Thesesynchronizing pulses are applied by the main oscillator which isadjusted for a frequency of twenty oscillations a cycle, as in: dicatedinFig. 2. With the oscillator 22*26 operating atnormal frequency, therewill be one effective synchronizing pulse a cycle, such pulsebeingapplied at an exact index point. With the oscillator22-2.6'operating at double the normal frequency, two synchronizingpulses will'be effective each cyclic period, such. pulses being eitherexact or mid-index point pulses. The other pulses, while reducing thegrid bias of the tube 26,. do not cause ignition of the tube becausecondenser 22is not applying the necessary ionizing potential at. thetimes such pulses are being applied, Manifestly, difierent synchronizingpulses. become effective when'the variable oscillator changes its phase.

For reasons which will be clear later, the oscillator. 22'e.-26e isrequired to generate oscillations at. half. the. normal frequency of thevariable oscillator; that is, to produce one oscillation every twocyclic. periods. It is desired, further, that such oscillation have anyof ten possible phases, although it may be mentioned that only nine ofthese. phases are utilized; namely, phases at.

index points 9. to 1. Oscillator 22e-2.6.c. thus,

requires synchronization at any of the index points of a cycle. Suchsynchronization is effected either by intermediate oscillator 22g-26g or22h-26h, depending on the position of switch S (Fig. 1). Eachintermediate oscillator is adjusted to a frequency of five oscillationsa cycle, but the oscillations of 22g2'6g are phased at even indexpoints, 8, 6, 4, 2, and D and those of 22h--26h at odd index points9,'7, 5, 3, and 1. Thus, a synchronizing pulse is produced by one or theother intermediate distributors at each index point. When the oscillator22e-26e is to operate at an odd index point phase, it is connected byswitch S to oscillator 22h-Z6h, as indicated at the right of Fig. 2where the arrows indicate the direction of flow of the synchronizingpulses or which of the oscillators are adapted to be synchronized byothers of the oscillators. When oscillator 22e26e is to have an evenindex point phase, switch S is shifted to connect it to oscillator22g2'6g for synchronization. With this arrangement, one pulse every twocyclic periods, produced either by 2'2g26g or 22h-26h is effective tosynchronize the oscillator 22e26e at its selected index point phase.

As previously explained, the intermediate osci1- lators are synchronizedby pulses from the main oscillator. Every fourth pulse produced at evenindex points by the main oscillator takes effect upon oscillator 2'2g26gto keep it synchronized, and every fourth pulse produced at odd indexpoints is effective to synchronize the oscillator Hit-25h.

Oscillator 22a26a, for reasons explained later, is adjusted to operateat a frequency of one oscillation every two cycles and at a D phase.This oscillator is locked in such phase by a pulse produced at the Dcycle point by intermediate oscillator 22g26g.

The foregoing has described, as an example, means whereby a primarysynchronizing meansthe main oscillator-produces twenty synchronizingpulses a cycle, the intermediate oscillators produce five such pulses acycle, the tertiary oscillators have a frequency of one oscillationevery two cycles, and the variable oscillator has a frequency of eitherone or two oscillations a cycle. It will be noted that all thesynchronized oscillators operate at submultiple frequencies of the mainoscillator, and the tertiary oscillators also operate at a submultipleof the frequency of the intermediate oscillators. Further, theoscillations of the synchronized oscillators may have any of a pluralityof different phases. By the means employed here and described above, allof the oscillators are maintained in locked or synchronized relationdespite their operations at various frequencies and phases, suchfrequencies, however, being in all cases submultiples of the mainoscillator frequency. The relations between the oscillators hold truefor different submultiple frequencies, other than those illustrated inFig. 2.

It is understood that the increment of synchronizing voltage acting onthe grid of a gas tube should be insufficient by itself to causeignition as, otherwise, there would be a tendency for the controlledoscillator to operate at the same frequency and in step with thesynchronizing oscillator. The increment of synchronizing voltage shouldbe such that when added to the normal voltage, there is a total gridpotential which is effective to fire the tube only upon condition thatthe potential across the condenser has attained a predetermined criticalvalue. The

resistances of the voltage divider to which the grid is connected and towhich the synchronizing pulse is applied are so proportioned that only asmall proportion of the pulse voltage is effective upon the grid.Considering oscillator 22g 26g, for instance, the resistance 393g has ahigher value than resistance 32g, so that the proportion of thesynchronizing pulse applied to the grid of tube 26g is relatively small.The condensers, such as 392g, further attenuate the synchronizingpulses.

It is well known that when the grid-controlled gas tube is ignited,there is grid current flow.- Since, in a relaxation oscillator, the timeduring which the gas tube is ignited is of the order of 1 microseconds,the current flow is in the nature of a steep pulse. As previouslyexplained, the two intermediate oscillators while having the samefrequency are to operate at different phases. As indicated in Fig. 2,the phase difference between these two oscillators is the cycle portionbetween two successive cycle points. It follows that as the gas tube ofone intermediate oscillator ignites, the anode potential of the gas tubeof the other intermediate oscillator is approximately one-half thedesired critical anode potential. Since, in the circuits, as shown inFig. l, the grids of the gas tube 26g and 26h are connected to a commonline 31H, there is a tendency for the pulse produced by grid currentfiow in one tube when ignited to raise the potential of the grid of theother tube. Such interaction, if allowed to occur, might throw theintermediate oscillatorsout of their desired phase relation by causingundesired pre-ignition of the gas tubes at lower than the desiredcritical anode potentials. Further both the intermediate oscil-' lators,by reason of their grid current flow, tend to react upon the mainoscillator to alter its frequency. Similarly, with switch S in positionop posite the one shown, there is a tendency for the oscillators 22a-26aand 22e26e to react upon each other as well as upon oscillator 22g-26g.In the shown position of the switch, oscillator 22e-26e tends to reactupon oscillator Hit-26h. Oscillator 2229 has a tendency toreact upon themain oscillator. To counteract these reactions and interactions, thegrid current pulses are almost completely attenuated. Part of suchattenuation is obtained by making the grid resistors 3| and My, 71,, a,and e as high in value as possible without affecting stability of theassociated gas tubes. Further attenuation is obtained by making theupper resistors of the voltage dividers, to which the grid resistors aredirectly connected, higher in value than the lower resistors; e. g.,resistor 393g is made larger in value than resistor 32g. Still furtherattenuation is effected by the condensers 302, 302g, 71., a, and e.

It may be mentioned that it is preferred to synchronize the tertiaryoscillators by the intermediate oscillators rather than by the mainoscillator because the tertiary oscillators thereby may be more readilyadjusted to their desired phase relations. This is because theintermediate oscillators together produce only one synchronizing pulsefor each possible phase of the tertiary oscillators.

Since the main, intermediate, and tertiary oscillators, once adjusted todesired frequencies, are to remain at these frequencies, the screengrids of their pentodes are connected to points of fixed potentials. Onthe other hand, it is intended to operate the variable oscillator at a7. base frequency or a multiple thereof; twice the base frequency in theassumed example; To enablethe variable oscillator to be varied infrequency, the screen grid of its pentode is connected to, a point whichis at either of two voltages. This point is in a control network whichwill now be described. I

The'control network includes a voltage divider comprised of resistors 29and 36. Resistor 30 is tapped at a, chosen point 550 by a connection tothe screen of pentode 23. A point 28, of this voltage divider isconnected to the cathode of a gas tube 55. The anode of this tube isconnected via a resistor 43 to a point 45 of a voltage divider comprisedof resistor 33, tube 39a, and selfbiasing resistor 592. The grid of tube55 is connected via a resistance 31 to a point 48 of a third voltagedivider comprised of resistor 40,

tube 42a, and self-biasing resistor 44. The resistances of the controlnetwork are so related that with tube 39a, at relatively high impedance,

tube 42a similarly at relatively high impedance,

and gas tube 55 shut off, the point 45 is near the potential of line I,point 28 is near the potential of line 2, and point 48 is still nearerthe potential of line 2. Under these conditions, the voltage differencebetween points 45 and 28is sufiicient to supply ionization potentialforv tube 55but the grid bias, which is the difference in potentialbetween points 28 and 48 is *sohigh as to prevent ignition of the tube.With the tube 55 in non-conductive condition, point 28 is at the lowerof two possible potentials and point 5500f resistor 31] also is at thelower of two possible potentials. The screen potential of'pentode 23 isthen relatively low and the tube impedance relatively high, causing thevariable oscillator to function at the lower or base frequency.

Assume that the frequency of the variable oscillator is to bemultiplied. Positive potential is applied, in a manner explained later,to the grid of tube 42a, reducing its bias and impedance, and, thereby,increasing the voltage at point 48. As a result, the grid bias of thegas tube 55 is lowered to such an extent as to cause ignition of the gastube. Current now flows from point 45 to point 28, raising the potentialat this point and at point 509. Consequently, the screen voltage ofpentode 23 is raised and the pentodes impedance reduced, causing thevariable oscillator to start operating at the higher frequency. In theassumed example, the variable oscillator values and the values of thecontrol network are so chosen and adjusted that, upon ignition of thegas tube 55, the frequency of the variable oscillator is doubled. It isunderstood thatv other multiples of the base frequency may be providedfor by suitable pre-adjustrnents of the circuitvalues. 7

Assume now that the variable oscillator is to be restored to operationat base frequency. In a manner described later, positive potential isapplied to the grid of tube 39a, reducing its grid bias anditsimpedance. Current flow inresistor 38 thereupon increases to such extentas to re. duce the potential at point 45 below the value required toapply ionization potential to gas tube 55. Hence, the gas tube isextinguished and points 23 and 500 return to their original lowpotentials and the impedance of the pentode 23-returns to its original,high value. Accordingly, the variable oscillator again functions at thebase frequency.

The firing pulse; that is, the pulse applied to the grid of the tube 42ato cause ignition of gas tube '55; is indirectly derived'from thetertiary oscillator 22a-26e. The shut-oil. pulse; that is, the pulseapplied to the grid of tube39a' to extinguish gas tube 55, is indirectlyderived; from the tertiary oscillator 22a-26a;

Considering first the oscillator 22a-25a, upon the breakdown of its tubea, there is an extremely rapid drop in potential across the resistor21a, causing discharge of a condenser 95,.which produces a sharpnegative pulse on resistor 95. The grid bias of tube 91a rises, reducingcurrent flow through resistor 58 and the tube. Point 99 thereupon risesin potential, charging up a con:- denser lilil to produce a positivepulse on resistor 44. This pulse has the same steep characteristic asthe pulse produced in resistor 21a upon break,-

down of the tube 26a. The positive pulse on'resistor is applied via wire44?) to the grid of. tube 39a, causing shut-off of gas tube 55..

Similarly, upon the breakdown of tube 26a of oscillator 22e25e,condenser E! discharges, pro:- ducing a steep negative pulse, onresistor 62, which is converted by the action-of the tube 6%, resistor54, and the condenser 66 to, a steep. positive pulse on a resistorfi'l.Assuming a switch 553 to be open, the positive pulse on resistor 61' istransmitted by wires 68 and 554 to the grid of tube 42a, causingignition of the gas tube 55.

In the present example, it is assumed that oscillator 2Za25a is adjustedto operate at half the base frequency of the variable oscillator 2225and that each oscillation has a D phase. Thus, at alternate D indexpoints, the oscillator 22a25a produces a shut-oil pulse, causing thetube 55, if ignited, to be shut off at such times. It'is assumed,further, that oscillator 22e26e is to have the same frequency asoscillator 22a26 a but that its phase shall-be adjusted to any of theindex points 9 to 1. cated in Fig. 2, the oscillator ZZe-Zfie has beenadjusted in one instance to produce a pulse at index point 5 of everytwo cycles and in the other instance to produce a pulse at index point 4of every two cycles. When the oscillator 22e.--26e is tobe adjusted toany odd index point phase, switch S is left in the position shown, inwhich case it will be synchronized by oscillator 22h-2 6h. When theoscillator 22e25e is tobe adjusted to an even index point phase, switchSis shifted to reverse position, so that the oscillator 226-266. will besynchronized by oscillator 22g.-25g,

As an example, assume the variable oscillator 2225 is to be shifted froma 6 phase to a D phase (see the next to last line of Fig, 2'). TheoscillatorZZe-Ziie is adjusted to the 4 phase and thereafter the switch593 (Fig. 1) is opened. Accordingly, the pulse produced on resistance 51at the 4 time of the first or second cycle following the opening ofswitch 503, will be applied via lines 68 and 554 to the grid of tube42a, causing ignition of the tube 55. The frequency of the variableoscillator 22--26.immediately doubles as indicated at point are of thenext to last line of Fig. 2. If the operation of the variable oscillatorwere permitted to continue at the doubled rate, its oscillations wouldbe in successive phases D and 5 as indicated by the dotted portion inthe next to last line, of Fig. 2. However, at the D time followingitsshift to a doubled frequency, the variable oscillator is restored tobase frequency operation. At this D time, the oscillator 22a-2fia causesa positive pulse to be produced on resistor 44, This pulse istransmitted via wire 44'!) to the grid of tube 390., as a result ofwhich the gas tube 55 is Thus, as indi- 9. 'shut off, restoring thevariable oscillator to'its base frequency. The quenching of gas tube 55,in the example under discussion, is coincident with the D phase of thedouble frequency oscillations, and the variable oscillator beginsimmediately to charge the condenser 22 at the reduced rate. The variableoscillator will then continue to operate at base frequency and itsoscillations will have a D phase until the next shift is effected.

A another example, assume the variable oscillator 22-26 is operating atbase frequency and at 8 phase and is to be shifted to a 3 phase. Theoscillator 22e-26e is adjusted to a 5 phase, as indicated in the upperof the two lines in Fig. 2 pertaining to this oscillator. The switch 503i then opened and the next discharge of the condenser 22c at the 5 timeproduces a positive pulse on resistor fill which is transmitted by wires68 and 5% to tube 420.. The gas tube 55 is thereupon ignited, and thevariable oscillator begins to operate at the double frequency, asindicated at point 5H of the bottom line of Fig. 2. At thi doubledfrequency, the oscillator 22-2E would be phased at 1.5 and 6.5, asindicated, partially in dotted lines, at the bottom of Fig. 2. At the Dtime following the change in its frequency, the oscillator 2226 isrestored to base frequency under'control of oscillator 22a26a in themanner described before. The variable oscillator will now generate thebase frequency oscillations at phase 3.

It should be understood that if the oscillator 22e26e has been adjustedto a particular phase, and switch 503 is re-closed after the phase ofthe variable oscillator 22-26 has been shifted once, the latter willremain in the shifted phase. Should it be desired to effect a differentphase shift, the oscillator 22e26e is adjusted according to the extentof the new phase shift and switch 503 is re-opened. If the oscillator22e-26e is adjusted to a particular phase, and switch 503 is left openfor a multiple number of two-cycle intervals, successive phase shifts ofthe variable oscillator will be effected, one shift every two cycles, toan extent determined by the phase of the oscillator 22e26e. Thus, ifthis oscillator is phased at 5 and the variable oscillator is initiallyin an 8 phase, the latter will be shifted first from the 8 phase to the3 phase (see the last line of Fig. 2), then from the 3 phase to the 8phase, and so on, one such shift occurring every two cycles as long asswitch 503 is left open.

As previously explained, the main oscillator supplies at least as manypulses a cycle as the possible number of phases of the variableoscillator when operating at the base frequency and the multiplefrequency, In the present instance, synchronizing pulses are afforded atintervals of half a cycle division; 1. e., at mid-index points and exactindex points. By supplying potentially effective synchronizing pulses atthis rate to the variable oscillator, the main oscillator assuresaccurate phasing of the variable oscillator when it is shifted from onefrequency to the other. Further, since the main oscillator also servesto synchronize the intermediate oscillators and, through them, thetertiary oscillators, it is assured that the control network willoperate in predetermined relation to the phases of the variableoscillator. Hence, the extent of phase shift of the variable oscillatormay be accurately controlled.

While there have been shown and described and pointed out thefundamental novel features of the invention as applied to a preferredembodiment itwill be understood that various omissions and substitutionsand changes in the form and details of the device illustrated and in itsoperation may be made by those skilled in the art, without departingfrom the spirit of the invention. It is the intention, therefore, to belimited only as indicated by the scope of the following claims.

What is claimed is:

1. In combination with an electrical oscillator circuit including avariable impedance determining by its value one or another of differentfrequencies of the oscillator circuit, a control network including agaseous discharge tube determining by its status one or another ofalternative electrical conditions of the network, means so operativelyassociating the control network with said impedance as to alter itsvalue and, thereby, the frequency of the oscillator circuit, upon achange in said electrical condition, meanssup plying a firing pulse tothe control network to fire the tube therein and thereby to change thecondition thereof, whereupon the frequency of the oscillator circuit ischanged, means supplying an extinguishing pulse to the network toextinguish the tube therein and return the network to its previouscondition, whereupon the oscillator circuit is restored to its previousfrequency, means for supplying synchronizing pulses to the oscillatorcircuit at a rate at least equal to one of said frequencies and amultiple of the different frequency, so as to lock the oscillatorcircuit at any of its frequencies in desired phase relation to a giventime base, and means for so timing the production of the firing andextinguishing pulses with respect to the operation of the oscillatorcircuit at any of its frequencies that the changes in-frequency of theoscillator circuit, resulting from changes in electrical condition ofthe network produced by the firing and extinguishing pulses, occur indefinite, known time base relation to the operation of the oscillatorcircuit at any of its frequencies.

2. In combination with a relaxation oscillator operable either at agiven frequency or double this frequency, said oscillator when operatingat a given frequency being phased at any chosen cycle point of a givencycle and when operating at the double frequency being phased either atany chosen cycle point or at any chosen midcycle point of the cycle,means responsive to an electrical pulsation for automatically shiftingthe frequency and hase of the oscillator, and means producingsynchronizing pulses and impressing them upon the oscillator at afrequency at least equal to th double frequency of the oscillator so asto lock the oscillator, while operating at either frequency, in anyphase or phases to which the oscillator is adjusted.

3. In combination with an electrical oscillator circuit adjustable tooperate at a given frequency or a multiple frequency, means includingelectronic discharge means responsive to an electrical pulsation forautomatically adjusting a constant or constants of the circuit to effecta transition from one frequency to the other or vice Versa, meansproducing synchronizing pulses at a rate at least equal the multiplefrequency, and means for impressing said pulses upon the circuit toassure fly-back operation of the circuit at definite phase times of achosen cycle while operating at either frequency and upon a transitionfrom either frequency to the other.

tio-ns to a given time base while operating at the given frequency andalso while operating at the multiple frequency, whereby upon thetransition in frequency of theoscillator circuit it is brought from onesaid locked phase relation to another I said locked phase relation. atthe new frequency.

s 5. In combination, a plurality of relaxation oscillators, e'achincluding a short-circuiting gas tube and a condenser applyinganode-to-cathode potential to the tube, each tube including a controlgrid responsive to a synchronizing pulse to ignite the tube whenrequisite anode-to-cathode potential is being impressed upon the tube oythe condenser, each said oscillator being adjusted to operate at adifferent phase or frequency, a synchronizing oscillator producingsynchronizing pulses, circuits commonly fed from the synchronizingoscillator for applying the synchronizing pulses to the relaxationoscillators, one circuit applying the pulses to the control grid of onerelaxation oscillator and the other circuit applying the pulses to thecontrol grid of another of the relaxation oscillators, and currentchoking means in said circuits to choke grid current produced in eachrelaxation oscillator upon ignition of the tube therein so as to preventsuch grid current ,in one relaxation oscillator from effectivelyreacting upon the grid of another said relaxation oscillator and so asto prevent said grid current in either oscillator from effectivelyreacting up on the synchronizing oscillator, whereby the frequencies andphases for which the oscillators are set remain undisturbed.

6. The combination with an electrical oscillator circuit includingelectrical control means variable in value to establish one or another.of different frequencies of the oscillator circuit, one frequency beinga multiple of the other, of a control circuit operatively connected tothe variable means and adjustable in electrical condition to so afiectthe value of the variable means as to produce a change in frequency ofthe oscillator circuit, means producing an electrical pulse andimpressing the pulse upon said control circuit to adjust its electricalcondition and thereby produce a change in frequency of the oscillatorcircuit, means impressing synchronizing pulses upon the oscillatorcircuit at a fixed frequency equal to at least the higher of saiddifferent frequena chosen cycle, and means so timing operation of thepulse producing means with respect to,op eration of the oscillator thatthe change in electrical condition of the control circuit occurs indefinite time relation to the operation of. the

j oscillator.

cies, so as to synchronize operation of the oscillator circuit at eachfrequency with respect to 7. In combination with an electricaloscillator circuit including electrical means variable in electricalvalue to cause a change'in operation of the oscillator circuitfromagiven frequ'encyto a different frequency, a control circuitoperatively connected to the electrical, variable means todetermine theelectrical value thereof and, thereby, to determine at which frequencythe oscillator circuit is operating, means for producing and impressingan electrical pulse upon said control circult to change its electricalcondition and thereby, through the variable means, "to change thefrequencyof the oscillator circuit, means apply ing synchronizingpotential to the oscillator circuit at a frequency which is at leastequal to'one of the frequencies of the oscillator circuit and a multipleof the different frequency, means for V applyingsynchronizingponentialto the-'pulserproducing means, and a pulsing meanselectrically coupled to both of the two aforementioned syns chronizingpotential applying means for locking both the latter means intosynchronism, whereb a change in condition of the control circuit occursin synchronized time relation to, phases of the oscillator circuit whileoperating atany of its different frequencies.

- ,7 8. The combination with a'relaxation oscillator including avariable impedance electronic discharge device determining by itsimpedance value a base frequency of the oscillator or an alternativefrequency thereof, said discharge device including control meansvariable in potential to vary the impedance value of the device, of a toits previous frequency-upon. a reverse change 7 in condition of thecircuit, one said frequency-being a submultiple of the other saidfrequency, a synchronizing oscillator producing synchronizing pulses ata frequency at least equal ,tothe higher of the two frequencies of theoscillator, and means applying saidsynchronizing pulses toaninput'circuit of the-oscillator so'as to synchronize it in relation to agiven time basewhile operating either at the higher frequency or thesubmu t le fr quency. s I i ARTHUR DICKINSON. 7

REFERENCES CITED I V The following references are of record in the fileof'thi's patent: 1 r

1 UNITED STATES PATENTS.

Number Name Date 2,266,516 Russell Dec. 16, 194-1- 2,1'3-2,e5.4 Oct.11,1938 ;j2 ,22 7,e1'5 7 Jan. 7,1941 2,113,165 I Young Apr. 5, 1938.2,-11'.'7,"58'7 'Young May 17, 1938 2,236,532

Gibb l Apr. 1, 194 1

